1. Field of the Invention
The present invention relates to a method for manufacturing memories, and more particularly, to a method for manufacturing two-bit memory cells.
2. Description of the Prior Art
Flash memory is a non-volatile memory. It can maintain stored information even without a power supply. Generally speaking, flash memory can be divided into two types of configurations, namely, a NOR flash memory and a NAND flash memory. The NOR flash memory is suitable for code flash memory mainly used for executing program codes. The NAND flash memory is suitable for a data flash memory mainly used for data storage.
FIG. 1 shows a structure of a two-bit flash memory cell according to the prior art. As shown in FIG. 1, the structure of the conventional two-bit flash memory cell comprises: a substrate 10, a gate insulating layer 12 comprising a silicon oxide layer 18, a silicon nitride layer 16, and a silicon oxide layer 14, wherein the silicon nitride layer 16 has two charge storage regions 16a, 16b and a control gate 20 is positioned on the gate insulating layer 12.
The two charge storage regions 16a, 16b of the above-mentioned flash memory cell are capable of storing two-bit data. However, as the size of electronic devices shrinks, the distance between the storage regions 16a, 16b becomes shorter which will result in complementary bit disturbance and other data storage problems.